1. Field of the Invention:
This invention relates to a pulse combustion apparatus which can be used effectively as a source of heat supply to, for example, a hot water supply system of the type in which heated water can be stored.
2. Description of the Prior Art:
There is known a pulse combustion apparatus having a combustion chamber in which a mixture of fuel gas and air repeats explosion and combustion in a pulsating way. This type of apparatus has, however, not been widely accepted for a number of reasons including the noise which results from its operation. A typical example of the known apparatus which has been proposed to solve the problem of noisy operation is shown in FIG. 7. It includes a muffler 2' provided between a fan F' and the top 1a's of an air pipe 1' in an air supply line A'. It also includes a muffler E' provided in an exhaust line C'. The muffler E' is located near the outer end of an exhaust pipe 12' and outside a hot water storage tank D'. The muffler E' is cylindrical and is nothing but a diametrically enlarged portion of the exhaust pipe 12'.
The apparatus as shown in FIG. 7 is, however, not a satisfactory solution to the problem of noisy operation. The noise which results from pulsating combustion in a combustion chamber 7' is transmitted to the fan F' through an air chamber 3' and leaks out of the fan F'. The casing of the fan F' does not have a wall thickness which is sufficiently large to suppress the noise. The pulsating combustion which occurs in the combustion chamber 7' proceeds by repeating, say, 80 to 100 cycles of air suction, explosive combustion, expansion and exhaust per second. The resulting noise substantially leaks out through the wall of the casing of the fan F' before it reaches the muffler 2'. Accordingly, the muffler 2' has only a greatly reduced effect of absorbing the noise. It is also to be noted that the casing of the fan F' produces resonance. Therefore, it is impossible to remove the noise effectively from the air supply line of the apparatus. The muffler E' provided in the exhaust line C' also fails to show any satisfactory noise damping effect, as is obvious from the results of theoretical analysis of experimental data which will hereinafter be described.
Another drawback of the known apparatus resides in its low thermal efficiency. Only the combustion chamber 7' and a tailpipe 9' are provided in the hot water storage tank D' for exchanging heat with water. The water in the tank D', therefore, exhibits a substantially large loss of heat.